1. Field of the Invention
The invention relates to an apparatus for the manufacture of corrugated pipes of thermoplastic plastics comprising circulating mold segment halves, which are disposed in two opposite rows subsequent to an injection head and of which two at a time combine along a straight molding path to form a closed hollow mold, and which, on their inside, have inside walls forming the corrugation, each of the mold segment halves, not connected with each other, of a row being guided out of the molding path substantially at right angles to the direction of production at the downstream end of the molding path by means of a return device, and being returned to the upstream end of the molding path along a return path, where they are again inserted in the molding path and attached to the mold segment half leading in the direction of production, the return device being a slide with a pivot arm, a coupling member being arranged on the free end of this pivot arm for the releasable coupling to a mold segment half, and drives being provided for continuously moving the coupling member from the downstream end of the molding path to the latter's upstream end and back again, and a wedge element being disposed at the downstream end of the molding path, separating the mold segment halves and cooperating with slopings disposed on the halves.
2. Background Art
An apparatus of the generic type known from U.S. Pat. No. 4,212,618 ensures that as low as possible a number of circulating mold segment halves is needed. The mold segment halves are separated from each other on the return path and returned at such an average speed that the return period for each mold segment half is less than the time needed by a half to move on the molding path by a distance corresponding to its length. This results in the saving of more than fifty percent of the mold segment halves as compared to conventional apparatuses of continuously circulating mold segment halves. There is but one mold segment half on each return path, which is piloted back to the upstream end of the molding path by continuous, accelerated and again decelerated motion. Owing to the low number of mold segment halves needed, the apparatus can be retrofitted for another diameter of pipe rapidly and at little expense, which is important in particular for pipes of extreme diameters, taking into account that in general only comparatively small quantities of such pipes are produced, there being little sense in preparing an entire apparatus for the manufacture of this pipe diameter. Such an apparatus will also provide for saving in the manufacture of special types of pipes as well as in the manufacture of transition pieces, sockets etc, these special types too only requiring a very limited number of the expensive mold segment halves.
U.S. Pat. No. 4,325,685 discloses an apparatus for the production of corrugated pipes of thermoplastic plastics, in which individual mold segment halves revolve continuously on two closed paths, two mold segment halves joining on a molding path to form a mold segment, and mold segments lying close by close to form a mold, in which a thermally plastic tube discharged by the injection head of an extruder or an injection-molding machine is molded to form a corrugated pipe. The individual mold segment halves have several different profiles, of which one at a time can be put into function. To this end, the mold segment halves are disposed on supports for displacement at right angles to their direction of movement and are moved into their working position by a shunt system. In this way even such mold segment halves can be engaged that mold a socket and/or a spigot of a pipe.
An apparatus for the manufacture of corrugated pipes of thermoplastic plastics is known from DE-G. 93 11 140 U1, in which the mold segment halves, contiguous by twos, are conveyed on a molding path by a driving pinion, which engages with a tooth profile on the lower side of the mold segment halves. The conveyance back is likewise effected by pinions, which are drivable to move sidewise, the mold segment halves thus being movable from the molding path to a return path and from the return path back again to the molding path. Subsequent to the pinions of sidewise conveyance, the return paths are provided with parking stations for mold segment halves that can be inserted in the return paths by their own drives. If a pair of mold segment halves, for instance for the molding of sockets and/or spigots on the pipe to be produced, is to be added to the molding path, then the corresponding additional mold segment halves are inserted in the return path and moved to the upstream end of the molding path, where they are added to the molding path. Simultaneously, a pair of mold segment halves, after being conveyed sidewise, is removed from the molding path at the downstream end of the molding path and prior to entering the return path, is moved into the parking position. If the additional mold segment halves are to be removed from the circuit, then the parked mold segment half is inserted in the respective return path directly prior to these additional mold segment halves being conveyed sidewise away from the molding path, so that the additional mold segment half can be parked again. As a result, the molding path has always the same length only such additional mold segment halves can be inserted that have exactly the length of the usual mold segment halves for the production of the corrugated pipe.